Artificial leather



June 27, 1933. A. c. SEWALL ARTIFICIAL-LEATHER Filed March 14, 1931 liu/enzfor 07W (1'. 5e wal' Patented June 27, 1933 UNITED STATES PATENT OFFICE I ARTHUR C. SEWALL, OF STONEHAM, MASSACHUSETTS, ASSIGNOR TO PAPER PATENTS COMPANY, OF NEENAH, WISCONSIN, A CORPORATION OF WISCONSIN ARTIFICIAL LEATHER Application filed March 14, 1931. Serial No. 522,605.

My invention relates broadly to leather substitutes and contemplates a synthetic or artificial material which has most of the desirable physical properties of leather, such as flexibility, strengths, ability to take a high luster or shine, and an appearance closely resemblmg that of leather. i

It is realized that many substitutes for leather. have been proposed in the past. Certain of these proposed substitutes contemplate the impregnation 'of various textile and fibrous materials with solutions and emulsions of various 'gums, the emulsions ineluding latex, an emulsion of gum balata, eaoutchauc, and other vegetable gums commonly known'as rubber. 1 It is believed, however, that by means of the improved features of my invention'ab'out to be described, I have succeeded in producing an article of manufacture which more nearly resembles leather in respect to the properties outlined above and others than duced. v

Broadly considered, my invention contemplates the impregnation of a' laminated fibrous material comprising a plurality of sheets of extreme thinness, such as tissue paper or the like with a solution of emulr sion of a gum such as rubber or the like, and

drying the thus impregnated material.-

' Referring to the drawing which shows a preferred embodiment of my invention 35 Fig. 1 is a perspective view of a mat for the improved-artificial leather forming the base material.

Fig. 2 is a cross-section thereof. Fig. 3 is a perspective of a leather-like 4 sheet suitable for a shoe insole, made in accordance with my invention, and Fig. 4 is a cross-section thereof.

I first prepare a inat 10 of the desiredthickness by superposing on each other a 4 plurality of thin tissue-like sheets 11. While the nature of these individual sheets may be greatly varied, I prefer to use a pure white sulphite paper stock. This tissue paper may.

- be made in the usual Way on a Fourdrinier 5 wire, run off onto a single drying roll and high tearing and tensile any article which has ever before been procreped by means of a doctor blade at a preferred ratio of about 1 to 2.2. In one of my preferred embodiments, in which a leather substitute suitable for shoe insoles is pro duced, I use a mat of forty to fifty plies of the crepes tissue above described. However, the number of, plies or sheets of tissue 1n the mat Wlll vary according to the desired sion, consisting of rubber dispersed in an 1 aqueous medium. I may use substantially an latex emulsion, either natural or prepare which is commercially available. Thus, I may use an emulsion having a concentration of solids inthe latex of forty-five to fifty per cent rubber or higher and which is of a creamy I consistency. I may dilute this emulsion before the impregnating operation with, say, about-thirty per cent water. I may also add stiffening materials such as casein or other suitable materials. Thus I may add about twelve ounces of casein to'a gallon of latex which contains about three and one-third pounds of rubber to the gallon, this material 4 being then diluted with about thirty per cent water. The solutionis preferably ammoniated or otherwise treated to render it stable and to prevent tackiness. There also may be added to the emulsion a suitable accelerator and also a vulcanizing agent if desired. The

proportions of ammonla or other suitable preservative and of the accelerator and vulcanizer, if such are used, need not be gone into, inasmuch as these are all matters which .are well known in this art.

' Briefly considered, my proceess consists in soaking the base material 10, comprising the laminated tissue sheets 11, described above,

with the rubber solution or emulsion, compressing the material to a desired thickness so as to compact the material and also to drain off the surplus solution or emulsion, if any, and then allowing thematerial to dry.

According to my preferred procedure, the impregnation is accomplished by placing the. base material in or on a press, trough, pan, or table, or on a belt or like conveyor, and then spraying the impregnating material upon it. "Sufficient latex is sprayed onto the upper surface of the material so that when the compressing step occurs it forces the impregnating material through substantially the entire mass of fibers, causing all of the laminations to adhere to each other and producing a substantially homogeneous mass, regardless of the number of plies which are used.

According to an alternative procedure, instead of using a press for compacting the material, I may employ a stack or set of rolls, the first pair of rolls touching very lightly and the subsequent pairs being graduated until the desired pressure on the last pair of rolls is the maximum required. The pressure on all the rolls must be regulated so as notto push or bunch the material, but to provide substantially the same pressure as would be obtained from two flat surfaces coming together.

The compressing operation is preferably carried out very rapidly and immediately following the impregnation step, in order to avoid setting of the rubber and consequent stickiness. It is not necessary that the pad be at first entirely saturated throughout its entire thickness, so long as, when pressure is applied, the liquid will be caused to impregnate substantially the entire thickness of the material and a substantial quantity, say at least about ten per cent thereof, will run off as a result of the pressure. Of course, the amount of material which is squeezed out increases with the amount of pressure applied. I have found that if toomuch pressure is applied, the finished material will not have the required strength, inasmuch as insufficient rubber will have been left in the fibrous material. I

I have found that water serves well to carry the latex through the base material and to deposit the rubber quickly therein, inasmuch as the water has atendency to move always ahead of the rubber.

The ratio of the base material to the rubber varies according to the type of product desired. For ordinary inner soles, the preferred proportions will be approximately fifty per cent of each, on a dry basis.

No particular type of equipment is necessary for carrying out my invention. Hence, I have not considered it necessary to illustrate or describe.any special apparatus. It ,is desirable, however, to avoid contacting the latex with most of the common metals,

particularly such metals as brass and copper, since not only does the latex stick to such metals but is chemically affected thereby. My best results have been obtained where the press plates, rolls, or other devices used for compacting the material have been covered with some material to which *the latex does not adhere and with which it does not combine chemically. Good results are obtained by coating the plate with an oil cloth surface, the oil side of the cloth facing the latex or base material, as the case might be. The oil cloth, if clean, does not stick to the material and produces ave'ry smooth surface, but it is necessary that the cloth be Washed prior to each pressing operation, inasmuch as the air causes whatever latex is left on the oil cloth to act as a cement which will adhere to the next batch. I have also successfully used over the plates a fine mesh wire, but this is in most instances notpreferred, inasmuch as a checked textile-like surface is imparted to the product by the wire. Another method of insuring against the'material sticking to the press or compressing rolls is to coat the latter with pyroxylin or other cellulose ester.

After the pressing operation the product is then ready for drying. This may be accomplished at room temperature or, if'it is deemed desirable or expedient, at a somewhat higher temperature. My preferred drying temperature is between 65 and 7t) degrees F. but may be considerably higher under certain circumstances.

Special care must be taken in handling the impregnated material when drying it. It is preferred to suspend the impregnated material in the drying atmosphere, but it is found that if the material is engaged at small surfaces, the heavy weight of the material is likely to result in tearing thereof. I have found that a satisfactory method of sus-, pending the material is to-engage it as by a pair of narrow laths or the like clampingly engaging the material on opposite sides adjacent an edge, and raising the sheet by this means. I have found that a pair of twoinch laths thi'is firmly engaging the material will adequately support a wet impregnated sheet as large as 24" x 90". The material is thus suspended in the drying atmosphere until dry, and is then cut into desired shapes or otherwise worked.

If desired for certain purposes, the base material may be reinforced either in one direction or in two directions, by including in the base material reinforcing filaments of various materials, such as cords or woven fibrous material.

Material made inaccordance with my invention has all the desirable properties of the various types of leathers, and may be used in lieu thereof. Thus, it may be of a soft suede-like quality or'have a sufficiently hard surface to qualify as an outer sole for or have properties lying between such shoes Such variations may be imparted extremes.

to the material according to the proportion of rubber to base material, the amount of compacting, and the nature of the treatment of the finished material. It will be understood that my product may be dyed and piration of the foot.

it is not necessary that the inner sole be so istics: Inner soles should be flexible and yet have enough firmness across the ball of the foot so that the edges will not curl after the shoe is stitched, as this causes open seams. In the manufacture of the artificial leather embodying my invention for this purpose, it will be desirable to provide a stiffening agent with the latex. However, care must be taken not to seal up the material, inasmuch as it must have sufiicient porosity to permit res- Furthermore, while strong that it cannotbe torn or picked apart, it must, nevertheless, have sufiicient strength to hold the stitching, inasmuch as the stitching machine operates very speedily and drives the thread and needle roughly, and also stitches very tight. The material must, therefore, be strong enough to stand these operations without being'torn by the thread.

In order to meet factory demands, I may provide my improved material in block patterns or in sheetform. The majority of the factories are equipped to die from the sheet. A preferred embodiment of my invention for this purpose comprises a base of 40 to 45 sheets of tissue paper of the type described above' impregnated with fifty per cent of rubber on a dry basis and compacted I as described. owever, these figures, as are the others in thisspecification, are given merely by way of example, and not as limiting.

Various other modifications and variations of my invention coming within the spirit of my invention will doubtless occur to those skilled in the art from the description herein given. Hence, I do not Wish to be limited to the specific details or embodiments disclosed herein except as set forth in the appended claims, which are to be interpreted as broadly as the state of the art will permit.

I claim as my invention:

or cut through 1. As a new article of manufacture, an artificial leather consisting of a pad of a plurality of superposed gossamer-like felted creped tissue sheets of cellulose fiberfeach sheet having a weight not substantially greater than approximately .05 of a pound per square yard, said pad being impregnated with rubber and compacted to provide a sub- .siantially homogeneous mat closely resembling leather in appearance, flexibility, strength. water-proofness, and adapted to accept a finish similar to leather.

As a new article of manufacture, an artificial leather consisting of a pad of about forty to forty-five sheets of creped felted cellulose tissue, each of not substantially greater than about .05 of a pound per square yard, said pad being impregnated with rubber and compacted to provide a substantially homogeneous .mat closely resembling leather in appearance, flexibility, strength, water-proofness, and adapted to accept a finish similar to leather.

ARTHUR C. SEWALL.

sheet having a weight CERTIFICATE OF CORRECTION.

Patent No. 1,915,339. 7 June 27,1933.

ARTHUR C. SEWALL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, lines 35, 36 and 37, strike out the words "for the improved artificial leather forming the base material" and insert instead "forming the base for the improved artificial leather"; and line 56, for "crepes" read "creped"; and that the said Letters Patent should be read with'these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 15th day of August. A. D. 1933.

M. J. Moore.

(Seal) Acting Commissioner of Patents. 

